Chain saw with gear drive

ABSTRACT

Disclosed herein is a compact, lightweight gear drive for a chain saw which includes a combination cutting chain sprocket and internal gear. The sprocket is in the form of a ring with a plurality of internal teeth which mesh with the teeth of a pinion gear located within the sprocket and driven by the engine. The sprocket has through recesses in its periphery to receive the drive tangs of the cutting chain. In one embodiment, the chain sprocket is supported in eccentric relation to the output shaft of the engine by a hub located interiorly of the internal teeth on the sprocket.

United States Patent Irgens [4 June 13, 1972 [54] CHAIN SAW WITH GEARDRIVE 3,519,037 7/1970 Linkfield ..l43/32 [72] Inventor: Finn T. Irgens,Milwaukee, Wis. mary Examine a1 d R. Schran [73] Assignee: OutboardMarine Corporation, Wau- Attorney-Robert E. Clemency, John W. Michael,Gerritt D. 1 Wi Foster, Bayard H. Michael, Paul R. Puemer, Joseph A.Gemignanio, Andrew 0. Riteris, Spencer B. Michael and [22] Filed: April3, 1970 Robert K. ceding [21] Appl. No.. 25,526 [5 A S ACT 52 us. Cl...143/3211, 74/438 Discbsed herein is ligmweiflh B drive M a 51 lm. Cl..B27b 17/08 chain saw which includes cmbinatin mini! chain 58 Field ofSearch ..143/32, 32 A, 32 B; 74/332, P and interim The spmcke i 3 74/438243, 243 SC ring with a plurality of internal teeth which mesh with theteeth of a pinion gear located within the sprocket and driven [56]References Cited by the engine. The sprocket has through recesses in itsperiphery to receive the drive tangs of the cutting chain. In NI E SATES P TENT one embodiment, the chain sprocket is supported in eccentricrelation to the output shaft of the engine by a hub located in- I,825, lI t i ly f th i l t th on th p k t 2,409,775 10/1946 Mall et al........l43/32 A l,773,288 8/1930 Valletta ..74/438 X 4 Claims, 5 DrawingFigures CHAIN SAW WITH GEAR DRIVE BACKGROUND OF INVENTION The inventionrelates to gear drives and more particularly to a gear drive for a chainsaw. Chain saws adapted for heavy cutting requirements require a geardrive to reduce the speed of the cutting chain while maintaining a highengine speed and maximum horsepower. Gear drives add weight and bulk tothe chain saw, and thus make gear drives unsuitable for the lightweightchain saws.

SUMMARY OF INVENTION The invention provides a compact gear drive for achain saw which provides adequate power for heavy cutting requirementsand which does not appreciably increase the weight of the chain saw. Thegear drive includes a combination gear and cutting chain sprocket in theform of a ring which has, along the outer periphery thereof, a pluralityof circumferentially arranged recesses which receive and drive the drivetangs of the cutting chain. In addition, the internal surface of thesprocket ring is provided with internal teeth which mesh with the teethof a pinion gear which is fixedly connected to the drum of a centrifugalclutch and is rotatably supported on the output shaft of the engine. Tominimize the size and diameter of the sprocket, the recesses areinwardly open and the pinion gear on the output shaft comprises two setsof axially spaced teeth separated by an annular groove. The drive tangsproject through the sprocket ring and are received in the annulargroove.

In one embodiment of the invention, the chain sprocket ring is supportedin eccentric relation to the axis of the output shaft by a bearing inthe fomr of a hub which is located interiorly of the chain saw sprocketand connected to the engine crankcase. The internal teeth of the chainsprocket ring ride on the outer bearing surface of the hub.

It is an object of the invention to provide a compact, lightweight geardrive for a chain saw which utilizes a combination chain saw sprocketand internal gear for transmitting power from the engine output shaft tothe cutting chain.

It is a further object of the invention to provide a gear drive for achain saw which provides the necessary power for heavy cuttingrequirements and which drive is lightweight, has a minimum of componentsand requires very little additional space.

Further objects and advantages of the present invention will becomeapparent from the following disclosure and accompanying drawings inwhich:

DRAI/VINGS FIG. 1 is a perspective view of a chain saw embodying thegear drive of the invention.

FIG. 2 is a fragmentary sectional view with portions removed of a geardrive in accordance with the invention.

FIG. 3 is an axially enlarged perspective view of the chain saw sprocketring shown in FIG. 2.

FIG. 4 is a perspective view of the output shaft gear shown in FIG. 2.

FIG. 5 is a plan view with portions removed in partial section of thegear drive shown in FIG. 2.

DETAILED DESCRIPTION In the drawings, FIG. 1 discloses a chain saw whichis generally designated 8 and which includes an engine 9 having anoutput shaft 1 l, and a cutter bar 10 which carries a cutting chain 12.The chain 12 conventionally includes a plurality of drive members ortangs 14 (FIG. 2).

Means are provided for transmitting power from the engine output shaft11 to the chain 12. In accordance with the invention, such means is inthe form of a combination chain saw sprocket and internal gear 18. Thechain sprocket 18 is in the form of a ring having, along the outerperiphery thereof, a plurality of outwardly open circumferentiallyarranged recesses 20 which receive and drive the chain. tangs 14. Theinside surface 22 of the chain sprocket 18 is provided with a series ofinternal teeth 24 which mesh with external teeth 26 on a gear 28. Thegear 28 is driven by the engine and, in the particularly disclosedconstruction, is freely rotatably supported on the output shaft 11 bybearings 30 and is fixedly secured to the drum 32 of a centrifugalclutch 34 (FIG. 5).

To minimize the diameter of the sprocket and thus the overall size andweight of the gear drive, the recesses 20 extend through the ring 18 andthe teeth 26 of gear 28 are arranged in two spaced rows 26a and 26b(FIG. 4) with the rows separated by an annular groove 36 which receivesthe bottoms 14a of the tangs 14, as shown in FIG. 5.

In accordance with the invention, means are provided for supporting thesprocket ring 18 in eccentric relation to the axis of the engine outputshaft and with the internal teeth in mesh with the gear 28 on the outputshaft. In the construction disclosed in FIGS. 2 and 5, the means formounting the sprocket ring 18 comprises a bearing or hub 38 which has aportion 40 located interiorly of the sprocket 18 and teeth 24. The outeror peripheral surface 41 of hub portion 40 serves as a bearing for thechain sprocket ring 18. The hub portion 40 includes an opening or notch46 (FIG. 2) through which the teeth 26 or gear 28 project and mesh withthe teeth 24.

Means are provided for connecting the hub 38 to the engine 9. Asdisclosed, the means is in the form of a mounting flange or boss 44 onthe engine 9. The hub 38 has a flange 45 (FIG. 5) which is supported onflange 44. The flange 45 is bolted or otherwise secured to the engine 9.

Oil is supplied to the chain 12 for lubrication thereof by meansincluding a passage 47 which extends axially in the hub or bearing 38and which communicates with another conduit or passage 48 extendingradially in the bearing 38 and terminating at the surface 41 in positionto supply oil to the recesses or voids 20 which are formed in thecombination gear and sprocket l8 and which receive the tangs 14 of thechain 12. As a consequence, oil is supplied to the tangs l4 and from thetangs to the cutter bar 12 and to the chain pivots.

It should be noted that in operation, the chain 12 exerts a pull orforce along the bottom edge of the cutter bar 12 in the generaldirection of arrow A incident to clockwise rotation of the combinationgear and sprocket 18. It should also be noted that the pinion or gear 28is located relative to the combination gear and sprocket 18 so as tolocate the line of action or pressure line between the meshed teeth soas to more or less oppose the direction of the arrow A. As aconsequence, the loading on the meshed teeth is relatively light and theloading on the bearing is reduced. In addition, the least possiblecouple is generated around the axis of the output shaft 11.

, Although the disclosed embodiment shows a chain sprocket driven by agear or pinion supported on the engine output shaft, the drive of theinvention can also be employed in other arrangements.

Various of the features of the invention are set forth in the followingclaims.

What is claimed is:

1. A chain saw comprising an engine, a shaft rotatably supported on saidengine and driven by said engine, a chain sprocket in the form of a ringincluding a plurality of outwardly open circumferentially arrangedrecesses adapted to receive the drive members of a cutting chain, andinternal teeth located on the inside of said ring and includingrespective inner end surfaces, gear means on said shaft, means forsupporting said chain sprocket on said engine in eccentric relation tothe axis of said shaft and with said gear means in mesh with saidinternal teeth, said means for supporting said chain sprocket on saidengine comprising a hub mounted on said engine and located interiorly ofsaid sprocket, said hub including a peripheral bearing surface engagedwith said inner end surfaces of said internal sprocket teeth and havingan opening through which said internal sprocket teeth mesh with saidgear means.

2. A chain saw in accordance with claim 1 wherein said gear meansincludes two spaced rows of teeth separated by an annular groove, saidgroove being adapted to receive the drive members of the cutting chain.

3. A chain saw in accordance with claim 1 wherein said hub includes anaxial passage and a radial passage connected to said axial passage, saidradial passage communicating with said recesses in said sprocket toafiord lubrication of the cutting chain 4. A chain saw comprising anengine, a shaft rotatably supported on said engine and driven by saidengine, a chain sprocket in the form of a ring including a plurality ofcircumferentially arranged recesses extending radially through said ringand being both radially inwardly and outwardly open, internal teethlocated on the inside of said ring, gear means on said shaft, means forsupporting said chain sprocket on said engine in eccentric relation tothe axis of said shaft and with said gear means in mesh with saidinternal teeth, and a saw chain trained around said sprocket andincluding drive tangs extending through said recesses and projectingfrom said recesses radially inwardly of said ring.

1. A chain saw comprising an engine, a shaft rotatably supported on saidengine and driven by said engine, a chain sprocket in the form of a ringincluding a plurality of outwardly open circumferentially arrangedrecesses adapted to receive the drive members of a cutting chain, andinternal teeth located on the inside of said ring and includingrespective inner end surfaces, gear means on said shaft, means forsupporting said chain sprocket on said engine in eccentric relation tothe axis of said shaft and with said gear means in mesh with saidinternal teeth, said means for supporting said chain sprocket on saidengine comprising a hub mounted on said engine and located interiorly ofsaid sprocket, said hub including a peripheral bearing surface engagedwith said inner end surfaces of said internal sprocket teeth and havingan opening through which said internal sprocket teeth mesh with saidgear means.
 2. A chain saw in accordance with claim 1 wherein said gearmeans includes two spaced rows of teeth separated by an annular groove,said groove being adapted to receive the drive members of the cuttingchain.
 3. A chain saw in accordance with claim 1 wherein said hubincludes an axial passage and a radial passage connected to said axialpassage, said radial passage communicating with said recesses in saidsprocket to afford lubrication of the cutting chain.
 4. A chain sawcomprising an engine, a shaft rotatably supported on said engine anddriven by said engine, a chain sprocket in the form of a ring includinga plurality of circumferentially arranged recesses extending radiallythrough said ring and being both radially inwardly and outwardly open,internal teeth located on the inside of said ring, gear means on saidshaft, means for supporting said chain sprocket on said engine ineccentric relation to the axis of said shaft and with said gear means inmesh with said internal teeth, and a saw chain trained around saidsprocket and including drive tangs extending through said recesses andprojecting from said recesses radially inwardly of said ring.